hollow stump of a tree, empty, thin
枵 centers on hollowness or emptiness, especially in a wooden context: a hollow tree stump, or more broadly something thin and insubstantial.
枵 combines 木 (tree) with 号, which likely contributes the sound and the idea of emptiness or hollowness. The exact historical development is uncertain.
A tree 木 with a hollow center like an empty call 号: the tree is just a thin, hollow stump.
For キョウ, imagine a hollow stump in Kyoto: Kyoto -> キョウ, and the stump is empty inside.